This invention relates generally to VHF/UHF antennas and particularly to VHF/UHF antennas that are intended for indoor use. With the recent adoption of television signal transmission standards for HDTV (High definition television) signals and ATSC (Advanced television systems committee) type signals, the need for significantly improved VHF/UHF antennas, primarily for indoor use, has become apparent. The most popular form of prior art VHF antenna was the ubiquitous "rabbit ears", which took up a great deal of space when fully extended and was difficult to adjust properly. Similarly, the "bow tie" UHF antenna was sensitive to adjustment and left a great deal to be desired in terms of performance. What is needed is an indoor antenna to replace both the rabbit ears and bow tie of the prior art and, hopefully do so with improved reception characteristics, since the transmitted signals are digital, which makes it imperative that signal reception be optimized to prevent data corruption.
Conventional VHF/UHF indoor antennas are limited in gain and directivity, and in some instances, very sensitive to the direction of the received signals. In an analog multipath environment, signal reflections and reduced gains are more tolerable in that, while the quality of the picture may be compromised, the viewer is presented with a viewable, though less than ideal, picture. With digital signals, these same signal impairments most often result in no viewable picture. Further, these transmitted digital signals require a lower voltage standing wave ratio (VSWR), between the antenna and receiver RF input terminals, than their analog counterparts and it is also very important to maintain a high signal to noise ratio.
Another draw back of the prior art rabbit ears and bow tie antennas was esthetic. The indoor antenna ideally should not be visible, or at least not look like the prior art devices. The combined antenna of the invention arranges the various elements such that the antenna may be conveniently packaged, in an unobtrusive way, with the television receiver. This is especially important due to the new, higher, aspect ratio of the picture tubes that are specially designed for HDTV receivers.
The combined Low VHF, High VHF and UHF antenna of the invention uses a UHF antenna as disclosed and claimed in the above-mentioned copending application in combination with a Low and High VHF antenna, in which the reflecting backplate of the UHF antenna also serves as a directing element for the VHF antennas. As fully discussed in the copending application, the increased width/length ratio of the UHF antenna improves its wideband performance, whereas the reflector guarantees a 10 to 15 dB front to back ratio in addition to providing excellent decoupling between the UHF output and the dipole elements. While the copending application also discloses and claims different configurations of active versions of the UHF antenna only a single version of the antenna is disclosed in the combination VHF/UHF antenna of the present invention. The inventive antenna also includes a "folded" dipole VHF element for enabling compact packaging of the antenna, without undue performance deterioration. The folded arrangement, for example, adapts itself for integration with HDTV television receivers that incorporate picture tubes of the new, higher, aspect ratio.